I am trying to view data from a database in an ExpandableListView (I am first trying to get it to work with hard-coded strings).
I used the following example: CodeWiki ExpandableListView
But I get a Runtime error when I click on a group to get a childView.
Categories1.java
public class CategoriesActivity1 extends Activity
{
ExpandableListView eListView; ExpandableListAdapter eListAdapter; ArrayList<String> groups; ArrayList<ArrayList<ArrayList<String>>> children; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.categories); eListView = (ExpandableListView)findViewById(R.id.expandableListView1); loadData(); MyExpandableListAdapter adapter = new MyExpandableListAdapter(this, groups, children); eListView.setAdapter(adapter); } private void loadData(){ groups= new ArrayList<String>(); children= new ArrayList<ArrayList<ArrayList<String>>>(); groups.add("Group 1"); groups.add("Group 2"); groups.add("Group 3"); children.add(new ArrayList<ArrayList<String>>()); children.get(0).add(new ArrayList<String>()); children.get(0).get(0).add("Child 1 group 1"); children.get(0).add(new ArrayList<String>()); children.get(0).get(1).add("Child 2 group 1"); children.get(0).add(new ArrayList<String>()); children.get(0).get(2).add("Child 3 group 1"); children.add(new ArrayList<ArrayList<String>>()); children.get(1).add(new ArrayList<String>()); children.get(1).get(0).add("Child 1 group 2"); children.get(1).add(new ArrayList<String>()); children.get(1).get(1).add("Child 2 group 2"); children.get(1).add(new ArrayList<String>()); children.get(1).get(2).add("Child 3 group 2"); children.add(new ArrayList<ArrayList<String>>()); children.get(2).add(new ArrayList<String>()); children.get(2).get(0).add("Child 1 group 3"); children.get(2).add(new ArrayList<String>()); children.get(2).get(1).add("Child 2 group 3"); children.get(2).add(new ArrayList<String>()); children.get(2).get(2).add("Child 3 group 3"); }
}
MyExpandableListAdapter.java
public class MyExpandableListAdapter extends BaseExpandableListAdapter
{
private ArrayList<String> groups; private ArrayList<ArrayList<ArrayList<String>>> children; private Context context; public MyExpandableListAdapter(Context context, ArrayList<String> groups, ArrayList<ArrayList<ArrayList<String>>> children) { this.context = context; this.groups = groups; this.children = children; } @Override public boolean areAllItemsEnabled() { return true; } @Override public ArrayList<String> getChild(int groupPosition, int childPosition) { return children.get(groupPosition).get(childPosition); } @Override public long getChildId(int groupPosition, int childPosition) { return childPosition; } @Override public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) { String child = (String) ((ArrayList<String>)getChild(groupPosition, childPosition)).get(0); if(convertView == null) { LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); convertView = layoutInflater.inflate(R.layout.categories_group, null); } TextView childTxt = (TextView)convertView.findViewById(R.id.TextViewChild01); childTxt.setText(child); return convertView; } @Override public int getChildrenCount(int groupPosition) { return children.get(groupPosition).size(); } @Override public Object getGroup(int groupPosition) { return groups.get(groupPosition); } @Override public int getGroupCount() { return groups.size(); } @Override public long getGroupId(int groupPosition) { return groupPosition; } @Override public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) { String group = (String) getGroup(groupPosition); if(convertView == null) { LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); convertView = layoutInflater.inflate(R.layout.categories_group, null); } TextView groupTxt = (TextView) convertView.findViewById(R.id.TextViewGroup); groupTxt.setText(group); return convertView; } @Override public boolean hasStableIds() { return true; } @Override public boolean isChildSelectable(int groupPosition, int childPosition) { return true; }
}
categories_group.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/categoriesLLayout2" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:id="@+id/TextViewGroup" android:layout_width="wrap_content" android:layout_height="50dp" android:layout_marginLeft="50dp" android:gravity="center_vertical" > </TextView> <TextView android:id="@+id/TextViewChild01" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginLeft="30dp" > </TextView> </LinearLayout>
Logcat:
03-17 15: 16: 13.468: E / AndroidRuntime (370): FATAL EXCEPTION: main 03-17 15: 16: 13.468: E / AndroidRuntime (370): java.lang.NullPointerException 03-17 15: 16: 13.468: E / AndroidRuntime (370): at nl.test.listing.activity.MyExpandableListAdapter.getChildView (MyExpandableListAdapter.java:64) 03-17 15: 16: 13.468: E / AndroidRuntime (370): in android.widget.ExpandableListConnector.getView (ExpandableListConnector.java:450) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.widget.AbsListView.obtainView (AbsListView.java:1430) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.widget.ListView.measureHeightOfChildren (ListView.java:1216) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.widget.ListView.onMeasure (ListView.java:1127) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.view.View.measure (View.java:8313) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android. view.ViewGroup.measureChildWithMargins (ViewGroup.javahaps138) 03-17 15: 16: 13.468: E / AndroidRuntime (370 ): on android.widget.LinearLayout.measureChildBeforeLayout (LinearLayout.java:1017) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.widget.LinearLayout.measureVertical (LinearLayout.javahaps86) 03- 17 15: 16: 13.468: E / AndroidRuntime (370): at android.widget.LinearLayout.onMeasure (LinearLayout.java:309) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.view. View.measure (View.java:8313) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.view.ViewGroup.measureChildWithMargins (ViewGroup.javahaps138) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.widget.FrameLayout.onMeasure (FrameLayout.java:250) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.view.View.measure (View.java : 8313) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.widget.LinearLayout.measureVertical (LinearLayout.java∗31) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.widget.LinearLayout.onMeasure (LinearLayout.java:309) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android .view.View.measure (View.java:8313) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.view.ViewGroup.measureChildWithMargins (ViewGroup.java data138) 03-17 15: 16 : 13.468: E / AndroidRuntime (370): at android.widget.FrameLayout.onMeasure (FrameLayout.java:250) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.view.View.measure ( View.java:8313) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.view.ViewRoot.performTraversals (ViewRoot.java:839) 03-17 15: 16: 13.468: E / AndroidRuntime ( 370): at android.view.ViewRoot.handleMessage (ViewRoot.java:1859) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.os.Handler.dispatchMessage (Handler.java:99) 03 -17 15: 16: 13.468: E / AndroidRuntime (370): at android.os.Looper.loop (Looper.java:123) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at android.app .ActivityThread.main (ActivityThread.javahaps683) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at java.lang.reflect.Method.invokeNative (native method) 03-17 15: 16: 13. 468: E / AndroidRuntime (370): in java.lang.reflect.Method.invoke (Method.java:507) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at com.android.internal.os .ZygoteInit $ MethodAndArgsCaller.run (ZygoteInit.java:839) 03-17 15: 16: 13.468: E / AndroidRuntime (370): at com.android.internal.os.ZygoteInit.main (ZygoteInit.java∗97) 03- 17 15: 16: 13.468: E / AndroidRuntime (370): in dalvik.system.NativeStart.main (native method)
I don’t know why I am getting this error by looking at an example, I just changed the xml values from px to dp.